Janus kinase 3 (hereafter referred to as JAK3) is a family of protein kinases. Although kinases in this family, other than JAK3, are expressed in a wide range of tissues, JAK3 is expressed locally in hematopoietic cells. This does not contradict the fact that JAK3 plays an important role in signal transmission via various receptors, such as interleukin (hereafter referred to as IL)-2, IL-4, IL-7, IL-9, IL-15, and IL-21 by noncovalent association with the common γ chain (refer to nonpatent literature 1 and nonpatent literature 2).
In XSCID (X-linked severe combined immunodeficiency) patient populations, JAK3 protein level lowers or a genetic defect is found in the common γ chain. It is indicated that this problem occurs because immunosuppression blocks JAK3-dependent signaling pathways (refer to nonpatent literature 3 and nonpatent literature 4). Animal experiments have shown that JAK3 not only plays an important role in maturation of B-lymphocytes and T-lymphocytes but also in maintaining the function of T-cells. Hence, it is expected that diseases involving proliferative abnormality of T-cells, such as rejection during organ/tissue transplantation and autoimmune diseases, can be treated by controlling immune response through this mechanism.
On the other hand, a pyrrolopyridine derivative (patent literature 1) represented by formula (A) or (B) or an imidazopyridine derivative (refer to patent literature 2) is known as a compound having JAK3 inhibition activity.
(For the symbols in the formulas, refer to the corresponding patent publications.)
Furthermore, a pyrrolopyrimidine derivative (refer to patent literature 3, patent literature 4, patent literature 5, and patent literature 6) represented by formula (C) is also known as a compound having JAK3 inhibition activity.
(For the symbols in the formula, refer to the corresponding patent publications.)
Still further, a pyrrolopyridine derivative (refer to patent literature 7) represented by formula (D) is also known as a compound having JAK3 inhibition activity.
(For the symbols in the formula, refer to the corresponding patent publication.)
However, in any literature, the compound according to the present invention is not disclosed specifically.    [Nonpatent literature 1] J. J. O'shea et al, Cell, Vol. 109 (suppl.), S121, 2002    [Nonpatent literature 2] K. Ozaki et al, Science, Vol. 298, p. 1630, 2002    [Nonpatent literature 3] P. Macchi et al, Nature, Vol. 377, p. 65, 1995    [Nonpatent literature 4] S. M. Russell et al, Science, Vol. 270, p. 797, 1995    [Patent literature 1] WO 2004/099205    [Patent literature 2] WO 2004/099204    [Patent literature 3] WO 99/065908    [Patent literature 4] WO 99/065909    [Patent literature 5] WO 01/042246    [Patent literature 6] WO 02/000661    [Patent literature 7] WO 2006/069080